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through the roots and leaves, converting it into 

 substances ready to form new parts of the plant. 

 These cells are placed irregularly, and not close 

 together, as the air is required to circulate round them. 

 The juices of these cells are readily seized by the 

 mycelium, and instead of going to the support of the 

 plant, they go to maintain the fungus. The mycelium 

 spreads throughout the plant, and finds its way to the 

 tubers. Here it travels between the cell walls, expands 

 the intercellular space, absorbs the contents of the 

 cells, and finally breaks them down, and the tuber 

 decays. Fig. 20 is an illustration by Professor 

 Marshall Ward, showing the mycelium attacking the 

 tuber, by running through the intercellular spaces, and 

 absorbing the contents of the cells. Figs. 24, 25, 26 are 

 other illustrations of the disease in tubers, by Mr. 

 Beaven. As the leaves are destroyed, the plant can 

 obtain no air internally, consequently no food is 

 assimilated, and the plant speedily dies. 



Perpetuation of the Disease. 



The manner in which the disease is perpetuated and 

 kept alive from one season to another, does not appear 

 to be satisfactorily agreed upon ; at any rate, different 

 methods are suggested. The manner in which the 

 disease is conveyed from plant to plant, however, is 

 satisfactorily determined. Mr. Worthington Smith 

 demonstrated some years ago that the disease was 

 carried on from year to year by means of resting 

 spores or ripened seeds, produced intersexually within 



